The present invention relates to an image forming method which comprises carrying out recording an image on an ink recording medium having a thermoplastic resinous layer on a support utilizing a pigment ink, and then at least heating the ink recording medium.
Ink jet recording is carried out in such a manner that minute ink droplets are allowed to jet utilizing various working principles, and to adhere onto a recording medium so that images and texts are recorded. Ink jet recording exhibits advantages of relatively high speed, low noise and the ease of multicolor formation.
Further, as a result of technical progress in recent years, the image quality of ink jet prints prepared by utilizing a dye ink have approached those prepared utilizing silver halide photography, and further, the price of such units has been reduced. As a result, ink jet printing has been increasingly employed.
Generally, dyes are soluble in solvents, and dye molecules are subjected to dying in either a molecular state or a cluster state. Accordingly, each dye molecule exists in a similar environment. Thus its absorption spectra have a narrow band and the resultant color is very pure as well as clear. In addition, since dyes exhibit no particle properties, neither light scattering nor light reflection occurs, resulting in high transparency as well as clear hue.
By contrast, however, when dye molecules are decomposed due to photochemical reactions and the like, the number of dye molecules decreases. Since the color density is proportional to the number of dye molecules, a decrease in the number of dye molecules results in degradation of light fastness. Ink jet recorded images utilizing a dye ink result in high image quality. However, the image quality markedly degrades during storage. Accordingly, the present situation is such that, in terms of image retention quality, no ink jet technique has yet developed which exceeds silver halide photography in that regard.
While competing with dye inks, employed as inks which are used to prepare images which results in desired light fastness are pigment inks in which pigments, which results in good light fastness, are employed as the colorant. Pigments are generally insoluble in solvents, and dye molecules form particles which result in color formation in a state dispersed in solvents. Even though molecules on the particle surface are subjected to decomposition due to photochemical reaction and the like, under the surface are dye molecule layers. As a result, apparent color results in minimum change so as to obtain good image retention quality. However, glossiness markedly degrades due to effects of scattered light, as well as due to reflected light of dye particles.
However, in images prepared by employing said pigment ink, since pigment particles are attached onto the medium surface, image quality results in degradation such as formation of bronzing, a decrease in glossiness, and the like. As a result, the quality of obtained images was inferior to that of conventional photography. In order to overcome the aforementioned problems, for example, methods in which latexes are incorporated into the ink are disclosed in Japanese Patent Publication Open to Public Inspection Nos. 6-145570 and 6-171072. The image quality obtained employing said method is improved compared to conventional one. However, glossiness as well as image quality has not reached a sufficient level, and specifically, bronzing in high density areas remains a major problem. Further, Japanese Patent Publication Open to Public Inspection No. 11-208097 discloses a technique in which, after a recording medium comprising a thermoplastic resinous layer as the outermost layer is recorded employing a pigment ink which does not comprise dispersing agents, pigment particles migrate into said thermoplastic resinous layer. In said patent, specifically disclosed as a method to facilitate migration of pigment particles adhered on the exterior surface of said thermoplastic resinous layer into said thermoplastic resinous layer is a method in which heating is carried out for 20 minutes while maintaining a temperature in the range of from 110 to 140xc2x0 C. When only such a heating treatment is carried out, said thermoplastic resin is fused, but the migration of pigment particles into said resin is not sufficiently accomplished and the surface is not sufficiently smoothed. Accordingly, resulting prints exhibit insufficient abrasion resistance as well as insufficient glossiness. In order to obtain sufficient abrasion resistance as well as sufficient glossiness, employing a pigment ink and media comprising said thermoplastic resinous layer, it is important that in the treatment after printing, pigment particles are sufficiently buried into the resinous layer.
Japanese Patent Publication No. 2-31673 discloses a technique regarding a recording medium resulting in excellent water resistance as well as excellent light fastness, which is comprised of a thermoplastic resinous layer as the outermost layer and an inorganic pigment layer as the adjacent layer. Even though the image durability is definitely improved employing the layer configuration in accordance with the aforementioned patent, no disclosure at all is made regarding ink jet recorded images produced by employing pigment ink, and no suggestion is made regarding the improvement of image performance which is obtained by application of not only heat but also pressure after recording, using an ink jet method.
An object of the present invention is to provide an image forming method employing a pigment ink capable of improving glossiness, abrasion resistance, and releasability during ink jet recording.
The aforementioned object of the present invention is accomplished employing embodiments described hereunder.
(1) An image forming method comprising jetting a pigment ink onto the ink jet recording medium comprising a support, and provided thereon, an ink receptive layer comprising thermoplastic resinous particles farthest from the support, by means of an ink jet method, applying heat and pressure simultaneously to the ink jet recording medium having the jetted ink.
(2) The image forming method of item 1 wherein the ink jet recording medium comprises a pigment ink solvent absorptive layer adjacent to said ink receptive layer.
(3) The image forming method of item 2 wherein the pigment ink comprises a dispersing agent.
(4) The image forming method of item 1, wherein heat and pressure is applied employing a heating roller.
(5) The image forming method of item 4, wherein the heating roller comprises a metallic cylinder and a silicone rubber roller.
(6) The image forming method of item 5, wherein the metallic cylinder contain a heating source inside of the metallic cylinder.
(7) The image forming method 4, wherein a nip width, formed by pressure between said metallic cylinder and said silicone rubber roller, is from 1 to 20 mm.
(8) The image forming method of item 1, wherein heating temperature of the ink jet recording medium is from 50 to 150xc2x0 C.
(9) The image forming method of item 4, wherein linear pressure resulted by said heating roller is from 500 to 3,000 N/m.
(10) The image forming method of item 1, wherein the thermoplastic resinous layer comprises a silicone emulsion in an amount of 0.5 to 10 percent by weight in terms of solid, or a water-soluble silicone compound in an amount of 0.5 to 10 percent by weight, with respect to the thermoplastic resinous particles.
(11) The image forming method of item 1 wherein glass transition point, Tg, of said thermoplastic resinous layer is higher than temperature at which said thermoplastic resinous particles are coated and dried during the production of said ink jet recording material, and is lower than the temperature at which said support is subjected to thermal modification due to said heating.
(12) The image forming method of item 2 wherein void volume of the ink receiving layer and the pigment ink solvent-absorbing layer is from 20 to 40 ml/m2.1. An image forming method wherein, after a pigment ink, comprising a dispersing agent, is adhered employing an ink jet method onto an ink jet recording medium comprising a support having as the outermost layer an ink receptive layer comprising thermoplastic resinous particles and a pigment ink solvent absorptive layer adjacent to said ink receptive layer, said fine thermoplastic particle ink receptive layer as the outermost layer is transparentized by a simultaneous application of heat and pressure to obtain an image.
The other embodiments of the invention are described.
1. An image forming method wherein, after a pigment ink, comprising a dispersing agent, is adhered employing an ink jet method onto an ink jet recording medium comprising a support having as the outermost layer an ink receptive layer comprising thermoplastic resinous particles and a pigment ink solvent absorptive layer adjacent to said ink receptive layer, said fine thermoplastic particle ink receptive layer as the outermost layer is transparentized by a simultaneous application of heat and pressure to obtain an image.
2. The image forming method described in 1. above wherein heat as well as pressure is applied employing a heating roller.
3. The image forming method described in 1. or 2. above wherein said heating roller is comprised of a metallic cylinder as well as a silicone rubber roller.
4. The image forming method described in any one of 1. through 3. above wherein a heating source is built into said metallic cylinder.
5. The image forming method described in any one of 1. through 4. above wherein a nip width, formed by pressure between said metallic cylinder and said silicone rubber roller, is from 1 to 20 mm.
6. The image forming method described in any one of 1. through 5. above wherein heating temperature resulting from said heating source, which is built into said metallic cylinder, is from 50 to 150xc2x0 C.
7. The image forming method described in any one of 1. through 6. above wherein linear pressure resulted by said heating roller is from 9.8xc3x97104 to 4.9xc3x97106 Pa.
8. The image forming method described in any one of 1. through 7. above wherein either a silicone emulsion or a water-soluble silicone compound is incorporated into said thermoplastic resinous layer in an amount of less than 1 percent by weight, with respect to the thermoplastic resinous particles.
9. In an image forming method in which after adhering ink onto an ink jet recording medium comprising a support having thereon a layer comprising thermoplastic resinous particles, employing an ink jet method, heating is carried out, an image forming method wherein the glass transition point, Tg, of said thermoplastic resinous layer is higher than the temperature at which said thermoplastic resinous particles are coated and dried during the production of said ink jet recording material, and is lower than the temperature at which said support is subjected to thermal modification due to said heating.
10. In an image forming method in which after adhering ink onto an ink jet recording medium comprising a support having thereon an ink receiving layer comprising thermoplastic resinous particles as well as a pigment ink solvent absorbing layer, heating is carried out, an image forming method wherein the void volume of said ink receiving layer as well as said pigment ink solvent-absorbing layer is from 20 to 40 ml/m2.